Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$44.57	8.552%	$48.3816	$48.38	$48.40	$48.40
Purchase #2	$129.40	12.188%	$145.1713	$145.17	$145.15	$145.20
Purchase #3	$161.34	8.754%	$175.4637	$175.46	$175.45	$175.50
Purchase #4	$119.85	7.246%	$128.5343	$128.53	$128.55	$128.50
Purchase #5	$94.42	5.320%	$99.4431	$99.44	$99.45	$99.40
Purchase #6	$50.54	5.442%	$53.2904	$53.29	$53.30	$53.30
Purchase #7	$205.57	12.775%	$231.8316	$231.83	$231.85	$231.80
7 purchase totals =	$805.69		$882.1160	$882.10	$882.15	$882.10